In Ethernet network architectures, devices connected to the network compete for the ability to use shared telecommunications paths at any given time. Where multiple bridges or nodes are used to interconnect network segments, multiple potential paths to the same destination often exist. The benefit of this architecture is that it provides path redundancy between bridges and permits capacity to be added to the network in the form of additional links. However to prevent loops from being formed, a spanning tree was generally used to restrict the manner in which traffic was broadcast on the network. Since routes were learned by broadcasting a frame and waiting for a response, and since both the request and response would follow the spanning tree, most if not all of the traffic would follow the links that were part of the spanning tree. This often led to over utilization of the links that were on the spanning tree and underutilization of the links that weren't part of the spanning tree.
To overcome some of the limitations inherent in Ethernet networks, a Provider Link State Bridging network (one example of a link state protocol controlled Ethernet network) was disclosed in application Ser. No. 11/537,775, filed Oct. 2, 2006, entitled “Provider Link State Bridging,” the content of which is hereby incorporated herein by reference. In a link state protocol controlled Ethernet network, the network elements exchange link state routing information to enable the network elements to compute shortest paths through the network. Because shortest path routing is used, a shortest path tree may be computed from each source node to avoid the use of the Spanning Tree Protocol, so that link utilization may be increased on the network. Additional details of conventional Ethernet networks and the manner in which a link state protocol controlled Ethernet network may be configured to operate are disclosed in the parent application which was incorporated herein by reference and, for brevity, will be largely omitted from this application. Although the parent application mentions the use of multicast on a link state protocol controlled Ethernet network, it still would be advantageous to provide a way to reduce the amount of forwarding state that is required to implement multicast on a link state protocol controlled Ethernet network.